Nanocrystalline　titanium　dioxide　(TiO2)　was　prepared　by　sol-gel　method　and　studied　at　eight　different　thermal　treatment　temperatures　ranging　from　373　to　1073　K.　The　resulting　material　was　characterized　by　transient　surface　photoconductivity,　XRD,　photoluminescence,　liquid-phase　photocatalytic　activity　and　other　characters.　The　photocatalytic　activity　of　these　catalysts　was　estimated　by　measuring　the　decomposition　rate　of　Rhodamine　B.　The　quantum　yield　of　(OH)-O-center　dot　production　during　TiO2　photocatalytic　process　was　estimated　in　aqueous　solution　using　terephthalic　acid　as　a　fluorescent　probe.　Analysis　of　the　photoconductive　spectrum　of　samples　has　revealed　the　existence　of　carriers　with　two　different　lifetimes　(tau(1)　and　tau(2)),　which　varied　with　the　sample　thermal　treatment　temperature　in　the　same　peculiar　fashion.　Both　of　the　photoconductive　carrier　lifetime　tau(1),　tau(2)　of　titanium　dioxide　and　liquid-phase　photocatalytic　activity　were　top　at　temperature　673　K,　and　bottom　at　temperature　473　K.　The　resistance　of　the　samples　was　also　found　to　be　maximal　at　thermally　treatment　temperature　673　K.　The　high　photoactivity　of　titanium　dioxide　at　temperature　673　K　can　be　explained　by　interfacial　charge-transference　between　anatase　and　rutile,　which　can　promote　the　separation　of　electrons　and　holes,　finally　leading　to　long　carrier　lifetime　and　large　resistance.　The　study　of　relationship　between　them　shows　carrier　lifetimes　may　be　used　as　a　new　way　to　measure　the　photoactivity　of　different　photocatalysts.　(c)　2006　Elsevier　B.V.　All　rights　reserved.